Gearless speed reducer or increaser

ABSTRACT

A gearless speed reducer or increaser consists of an input shaft, an output shaft, and a motor connected to the input shaft. There is an external race connected to one of the shafts, and an internal race attached to the other shaft. Two ball bearings are disposed between the races. After the ball bearings have been inserted, the shafts are tilted relative to each other so that the balls become fixed in pockets created between the races and cannot slide within the races. Rotating one of the shafts thus rotates the other shaft, since the balls do not slip but only rotate between the races. The system acts as a speed reducer or increaser due to the different diameters of the inner and outer races. The system can be uncoupled by pivoting the shafts back into alignment so that the balls can slide freely within the races.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119(e) of U.S. ProvisionalApplication Ser. No. 60/927,134, filed on May 1, 2007.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a gearless speed reducer or increaser. Inparticular, this invention relates to a device that transmits rotationalpower from an input shaft to an output shaft, so that the second shaftrotates at a greater or lesser speed than the input shaft, using a setof ball bearings, and without using gears.

2. The Prior Art

In traditional devices used to increase or reduce speed, the connectionbetween the input shaft and the output shaft is made through the use ofgears. An internal gear on one shaft cooperates with an external gear onthe other shaft to transmit the power from one shaft to the other. Ifthe two shafts have different radii, the speed of one shaft will differfrom that of the other shaft.

A problem with this arrangement however, is that it is very difficult tocreate precisely machined gears that have no play between them. Thisplay leads to inaccuracies in the machine in which the shafts aredisposed. With operations that require very precise positioning, such aswith jewelry making or circuit board operations, the traditionalgear-based speed reducers are not optimal.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a speed reducer orincreaser that can achieve very precise tolerances. It is another objectof the invention to provide a speed reducer or increaser that can beeasily manufactured with few parts.

These and other objects are achieved by a gearless speed reducer orincreaser comprising an input shaft, an output shaft, a and motorconnected to the input shaft. There is an external race connected to oneof the shafts, and an internal race attached to the other shaft. Twoball bearings are loosely disposed between the races. After the ballbearings have been inserted, the shafts are tilted relative to eachother to form a pocket for the balls so that the balls are held inplace, and cannot slide around within the races. The pocket is formed bythe tilting of the races, and the curvature of the inner and outer raceswith respect to each other. The pockets are created by reducing theclearance on either side of the ball via the tilting so that the ballcannot move out of its current position. Rotating one of the shafts thusrotates the other shaft, since the balls do not slip when they areconfined within the pocket between the races. Instead, the rotation ofthe input shaft causes the ball bearings to rotate, which in turn rotatethe output shaft in the opposite direction. The ratio of the diameter ofthe inner race to the outer race is what determines the degree of speedreduction or increase. The greater the size difference between the innerand outer race, the greater the speed reduction (or increase). If theouter race has an inner (contact) diameter of twice the outer (contact)diameter of the inner race, then the speed ratio of the inner race tothe outer race will be 2:1.

The system can be uncoupled merely by pivoting the shafts back intoalignment so that the balls can rotate freely within the races.

The amount of tilt required to engage the shafts with each other dependson the amount of play existing between the races and the balls. Theshafts are tilted just enough to capture the balls so that they stay inplace. The tilt occurs around an axis running through both of the balls,and through a center of the races. This axis is perpendicular to thelongitudinal axis of the shafts.

The inner race can be mounted on either the input shaft or the outputshaft, depending on whether the system is used as a speed increaser orreducer. For speed reduction, the inner race is mounted on the inputshaft. For speed increase, the outer race is mounted on the input shaft.Once the proper tilt angle is created, the shafts can be fixed in placeto guarantee smooth power transmission. Speed reduction takes placebecause one rotation of the input shaft causes only a fractionalrotation of the output shaft, due to the larger diameter of the outerrace.

A system can be set up using two of the transmission arrangements,arranged on either end of an intermediate shaft. The input shafttransmits power through the first transmission arrangement, which causesthe output shaft to rotate. This output shaft forms part of anintermediate shaft and is connected to a second transmissionarrangement, which then transmits power to the final output shaft of thesecond transmission arrangement. By using two transmission arrangements,a maximum amount of speed reduction can be achieved, and the angles ofthe two transmission arrangements can be set so that the input shaft andthe final output shaft are rotating parallel to each other. Theintermediate shaft can be constructed as a hollow sleeve into which theoutput shaft of the first speed reducer is inserted. The input shaft ofthe second transmission arrangement is inserted into the other end ofthe sleeve.

The shafts are held in place in the sleeve against rotation. This can beaccomplished in several ways. In one embodiment, the shafts and sleeveare equipped with a series of ball tracks, into which ball bearings aredisposed. The ball bearings hold the shaft against rotation in thesleeve. In another embodiment, a keyway is provided. The sleeve can beprovided with a longitudinal ridge that slides within a longitudinalgroove in the shaft, or vice versa. This also prevents rotation of theshaft within the sleeve. While rotation relative to the sleeve isprevented, the shafts are able to move longitudinally within the sleeveto obtain the proper tension on the speed reducers. This tension isaccomplished by springs, which press the shafts and their associatedraces against the corresponding races in the speed reducers. Thisensures that the rotational motion is transmitted through thetransmission arrangement, and prevents any slippage by the balls in thetransmission arrangement. The sleeve is also preferably equipped withstop elements that prevent excessive axial movement of the shafts withinthe sleeve.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and features of the present invention will become apparentfrom the following detailed description considered in connection withthe accompanying drawings. It is to be understood, however, that thedrawings are designed as an illustration only and not as a definition ofthe limits of the invention.

In the drawings, wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 shows a top view of the transmission arrangement according to theinvention, with the ball bearing shown in dotted lines;

FIG. 1A shows a cross-sectional view of the inner and outer races ofFIG. 1;

FIG. 2 shows a side cross-sectional view of the transmission arrangementof FIG. 1;

FIG. 2A shows a perspective view of the arrangement shown in FIG. 2;

FIG. 3 shows a top cross-sectional view of the transmission arrangementof FIG. 1;

FIG. 4 shows a side cross-sectional view of the transmission systemaccording to the invention;

FIG. 5 shows a cross-sectional view along lines V-V of FIG. 4;

FIG. 6 shows a cross-sectional view of an alternative arrangement of theshaft and sleeve; and

FIG. 7 shows a top view of the transmission system according to theinvention shown in FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now in detail to the drawings, FIG. 1 shows a top view of thetransmission arrangement according to one embodiment of the invention.The transmission arrangement 1 comprises an input shaft 10, connected toan inner race 15, and an output shaft 11, connected to an outer race 16.Between the two races are two ball bearings 14, shown in dotted lines inthis view. A motor 20 is connected to input shaft 10. Inner race 15 isdisposed angularly offset to outer race 16, so that ball bearings 14 areheld in a pocket between the races with no play. The offset occurs bypivoting one of the races around the y-axis shown in FIGS. 2-3. Thedegree of offset required to hold the balls depends on the curvature ofthe raceways, the size of the balls, and the amount of play of the ballsin the races prior to being offset. This pivoting creates a pocket toaccommodate the balls, and reduces the clearance on both sides of eachball 14 to eliminate the ability for the ball to slide along the races.Balls 14 are held in the races 180 degrees apart at all times, and thepivot or offset of the races takes place around an axis created by balls14. Rotation of input shaft 10 causes output shaft 11 to rotate, but ata different speed. The speed reduction or increase is directly dependenton the ratio between the diameters of the inner and outer races.

FIG. 2 shows a side cross-sectional view of transmission arrangement 1according to the invention, and FIG. 3 shows a top cross-sectional view,which is the same view shown in FIG. 1. FIG. 2A shows a perspective viewof the transmission element 1. Here, it is clearly shown that outer race16 is pivoted with respect to inner race 15. This pivoting takes placearound the Y axis, to form pockets for balls 14. The twisting of theraces cuts off access to the rest of the ball cage, to prevent the balls14 from sliding around within the races.

FIG. 1A shows a detailed view of the speed reduction/increase mechanism.In the views shown in FIGS. 1-3, the device is a speed reducer. In thisdevice, inner race 15 is connected to input shaft 10 and outer race 16is connected to output shaft 11. Rotation of inner race 15 by motor 20causes bearings 14 to rotate as well, since they are held within thepocket created between inner race 15 and outer race 16 without anyslippage. In turn, rotation of bearings 14 then causes outer race 16 torotate, and consequently outer shaft 11, to which it is coupled. Thedegree of rotation of outer race 16 is less than the degree of rotationof inner race 15, due to the different diameters of the two races. Thegreater the difference between outer contact diameter d of inner race 15and inner contact diameter D of outer race 16, the greater the degree ofspeed reduction or increase. The inner and outer contact diameters arebased on the diameters of the inner and outer races where each contactsball bearing 14.

Pivoting races 15 and 16 so that shafts 10, 11 are parallel to eachother releases ball bearings 14 and stops the transmission of power. Thesystem according to the invention has great advantages over conventionalgear transmissions, because there is virtually no slippage between theraces once the shafts are rotated to capture the balls in place.Furthermore, since there is no slipping or rubbing, wear on the ballsand races is minimal.

FIGS. 4 and 7 shows an embodiment of the transmission arrangement in atransmission system having two of the above-described transmissionarrangements. In the system, output shaft 11 of one transmission system,which is connected to outer race 16, is connected via a hollow sleeve 30to a second transmission system 2, having an input shaft 39 and an innerrace 17. Inner race 17 is then coupled via ball bearings to an outerrace 18 and a second output shaft 40, as shown in FIG. 7. As shown inFIG. 4 and in the cross-sectional view shown in FIG. 5, shafts 11 and 39are held within sleeve 30 so as not to rotate, by a series of ballbearings 27 that roll within cut-out channels 28 and 29 of shafts 11, 39and sleeve 30, respectively. This arrangement allows shafts 11, 39 toslide axially within sleeve 30 (i.e., along longitudinal axis A) and yetonly rotate together with sleeve 30. As an alternative, channels 28 and29, a keyway arrangement can be provided, such as shown in FIG. 6. Here,instead of channels and balls, the shafts are held in place againstrotation by a ridge 34 connected to sleeve 30, and a groove 19 cut intoshaft 11 or 39. Ridge 34 slides within groove 19 and allows axialmovement, but not rotation relative to sleeve 30. To prevent excessiveaxial motion of shafts 11, 39, a stop mechanism formed of protrusions33, 34 is arranged between shafts 11, 39 and sleeve 30. Protrusions 33limit the motion of shafts 11, 39 to the distance between protrusions33, as protrusion 34 cannot pass the barrier formed on either side byprotrusion 33. Other methods of limiting the axial motion could also beused.

Sleeve 30 is held in place by roller bearings 31, 32. Other means forholding sleeve 30 in place may also be used, such as a cage with ballbearings, slide bearings, or any other suitable arrangement that allowssleeve 30 to rotate when motor 20 is running.

To ensure proper pressure on transmission arrangements 1 and 2, to keepthe races in proper positioning, a spring 25 may be used, as shown inFIGS. 4 and 7. Spring 25 acts on races 16 and 17, to press them againstraces 15 and 18, respectively to ensure proper engagement of ballbearings 14. Spring 25 rests against a stop 42 on sleeve 30. Other meansof ensuring pressure of the races against each other could also be used.

As shown in FIG. 7, by using two transmission arrangements 1, 2, theshafts can be positioned so that second output shaft 40 is parallel toinput shaft 10, thus avoiding any potential complications from havingthe shafts be set at an angle to each other. The dual transmissionarrangement also allows for twice the speed reduction or increase. Thesystem of the present invention provides for very precise rotationalmotion transmission, with virtually no play between the shafts. Thismakes the system of the present invention ideal for uses that requirevery accurate positioning of parts, such as in jewelry making, circuitboard manufacturing, and many other industries. Furthermore, the systemaccording to the invention is simpler to construct and does not weardown as quickly as gear-based systems, thus saving cost and maintenancetime.

Accordingly, while only a few embodiments of the present invention havebeen shown and described, it is obvious that many changes andmodifications may be made thereunto without departing from the spiritand scope of the invention.

1. A transmission arrangement comprising: an input shaft; an outputshaft; an outer race mounted on one end of one of the input and outputshafts; an inner race mounted on one end of the other of the input andoutput shafts, the inner and outer races being arranged concentricallyto create a cage for ball bearings; at least two ball bearings disposedwithin the cage 180 degrees apart from each other; wherein the races arepivoted with respect to each other around an axis running through eachof the balls such that the balls are captured in a pocket between theraces and cannot slide within the races, and so that rotation of theinput shaft rotates the output shaft at a different speed than a speedof the input shaft.
 2. The transmission arrangement according to claim1, wherein the inner race is disposed on the input shaft and the outerrace is disposed on the output shaft.
 3. The transmission arrangementaccording to claim 1, wherein the outer race is disposed on the inputshaft and the inner race is disposed on the output shaft.
 4. Thetransmission arrangement according to claim 1, further comprising amotor connected to the input shaft for rotating the input shaft.
 5. Asystem for transmitting rotational power, comprising at least twotransmission arrangements according to claim 1, said transmissionarrangements being connected to each other via an intermediate coupling,wherein rotation of the input shaft of the first transmissionarrangement transmits rotational power through the two transmissionarrangements to the output shaft of the second transmission arrangement.6. The system according to claim 5, wherein the intermediate couplingcomprises a hollow sleeve having two ends, the output shaft of a firstone of the transmission arrangements being disposed in one end of thehollow sleeve and the input shaft of a second one of the transmissionelements being disposed in the other end of the hollow sleeve.
 7. Thesystem according to claim 6, wherein the output shaft of the firsttransmission arrangement and the input shaft of the second transmissionarrangement are coupled to the hollow sleeve so that the shafts can movealong a longitudinal axis of the sleeve, but not rotate relative to thesleeve.
 8. The system according to claim 6, further comprising apressure element connected to one side of each of the transmissionarrangements to press the races against one another.
 9. The systemaccording to claim 8, wherein the pressure element is a spring.
 10. Thesystem according to claim 7, wherein the output shaft of the firsttransmission arrangement and the input shaft of the second transmissionarrangement are equipped with longitudinal grooves, and the hollowsleeve is equipped with corresponding longitudinal grooves, and furthercomprising ball bearings disposed in the spaces created by thelongitudinal grooves of the shafts and the hollow sleeve, to allow theshafts to move axially, but not rotate within the sleeve.
 11. The systemaccording to claim 7, wherein the hollow sleeve is equipped with alongitudinal ridge, and the output shaft of the first transmissionarrangement and the input shaft of the second transmission arrangementare each equipped with a longitudinal channel, wherein the ridge slideswithin the channels to allow axial movement of the shafts withoutrotational movement relative to the sleeve.
 12. The system according toclaim 7, further comprising a stop mechanism located on the hollowsleeve to prevent axial movement of the output shaft of the firsttransmission arrangement and of the input shaft of the secondtransmission arrangement beyond a predetermined limit.
 13. The systemaccording to claim 6, further comprising a bearing arrangement disposedaround the hollow sleeve, to support the hollow sleeve and allowrotation of the hollow sleeve.
 14. The system according to claim 13,wherein the bearing arrangement comprises at least two roller bearings.